Process for recovering sulfur.



A. F. HQFWMN PROCESS FOR RECOVERING SULFUR.

APPLICATION FILED APR. 8. I916.

31 ,wfi ww Patented M 23, 1918.

WITNESSES ATTORNEY PUCESS TUE. UVENG SULFUR,-

fo all whom a may concern."

Be it known that l, hnnisorr F. Horriran, a citizen of the United States, residing at Pittsburgh, in the county of Allegheny and State of Pennsylvania, have invented oertain new and useful Improvements in Processes for Recovering Sulfur, of which the following is a specification.

My invention relates to a process for recovering sulfur and ore from metallic s11 l' fids or pyrites such as arei'usually wasted in connection with mining of coal.

ft is a known fact that most of these sulfids' contain approximately one-half sulfur and therefore the primary object of the present process consists in the recovery of the sulfur from the above mentioned'sulfids, the ore being a by product of the process. With the above and other objects in view, ll will now proceed to describe my process in connection with the preferred form of apparatus for carrying out the same.

Figure 1, is a diagrammatic View illustrating' the elements of the apparatus in which my process is carried out, and Fig. .2, is a View in section of a retort chamber.

The apparatus as shown in the accompanying'drawing consists of the retort A having the chamber 13 closed at the top by the cover U and the opening at the bottom 7 provided with grates 1D. This opening leads into a pit E in which a screw conveyer it? works, such .conveyer being driven by any suitable means such as G. This conveyor dumps onto a second conveyer Hwhich may be of any suitable bucket type to relieve the 1 conveyor 15 of its material and remove the door U and at the top by door V. i

same from the vicinity of the retort. The back of. the retort is apertured as at-ll and covered by a door J provided with suitable air holes which may be plugged if desired. Through this aperture l the combustion in the retort may be started. Further apertures K are provided which communicate with a passage L closed by an observation door M. Both the passage 1L and steam pipe N enter the chamber B. At the top of the retort chamber B the conduit 0 leads'out and terminates inv the conoidal top P of the collector Q provided with the opening lit through which contents thereof may be removed, The top P of the collector Q is provided with an outlet conduit S which leads into the bottom of a condenser and washer T, said washer being closed at thebo'ttom by Specification of Letters Patent. M m arm yy a lication filed April a, rare. Serial No. eater. I

washer is filled with coke or stone W which may be sprinkled with water through the medium ef-the sprinkler head X supplied by pipe Y. At the bottom the condenser tilland washer T is provided witha grating S directly over a pit h which is relieved of its contents through a suitable conveyer B having buckets C. The operation of the apparatus is as follows:

Suppose the retort chamber B is. to be charged with a metallic sulfid having the chemical formula lBeS and that combustion is started in the presence of ample oxygen.

The reaction taking place will be as follows:

Thus oxid of ironremains after reaction and the vapors given of are sulfur dionid.

The sulfur 'dioxid is conveyed through the.-

conduit 0 to the dust collector Q, which separates any dust fromv the gases, and thence the vapors proceed to the, condenser and washer T where they are acted on by the water and a little of the sulfur dionid dis- 1 i solved in the Water produces sulfnrous acid.

The continuance of the process is regulated by the speed of the conveyer F which regu- .lates the rate of combustion within the retort ii. That is to say, as the refuse or meit reach such a temperature the sulfids would fuse.

When the sulfids are charged into retort chamber lB, provided sufficient oxygen is not present to assist combustion to the extent indicated in the previous paragraphs, the following reaction may take place:

lit will .be seen by this reaction that the metallic oxid remains while sulfur dioxid and pure sulfur fumes pass over.

In treating pure pyrites such as contains 58.3% sulfur and 46.7% iron the combuslllltl llllll .tion will take" place without the addition of 'fuel once th'egfire is started as this compound has approximately.tliree-eighths the masses and bands it is impracticable tofirst 'olean it and then burn it as'it usually contains a little-coal and therefore the same is 'used in its original form since the. coal biirns and leaves comparatively little ash in no wayinterferin with the process. Of course a'little' sul r may unite with carbon monoxid under certain conditions to form carbon COS, but this is more than compensated for by a subsequent reaction which occurs and I which follows:

. Fes+0+CO =Fe,G0 -s.

' FeS +O+C0 =Fe CO +2S The carbonate of-iron formed decomposes lower down in the retort and the effect of thesmall amount of coal clinging to marcasite'pyrite is to produce an increase in the quantity of sulfur discharged, the quantity of sulfur dischargedbeing in the neighborhood of 60% in the form of sulfur gas and 40% sulfur dioxid. With marcasite pyrite the quantity of coal adhering to the pyrite is usually in the neighborhood of 10. and 15% and since sulfur volatilizes at 450 C. and distils from a metallic sulfid at approximately 7 00 (lthe temperature of the retort chamber B must be held within the range indicated, and as before stated must in no instance reach or exceed 900 C. To hold the retort chamber B within the proper temperature limits the oxygen supply must be carefully regulated and a pyrometer is absolutely essential.

In carrying out this process steam may be admitted to the retort B as indicated in the drawings of the apparatus and the addition of this steam acts differently according to the temperature of the retort at the time of admission. If the retort chamber B is operated at a temperature above 700. C. the pyrite can be almost completely desulfurized by the use of steam, usually only 1 to 3% of sulfur remaining in the ores, whereas the gas given off will consist principally of sulfur vapors, carbon dioxid, nitrogen, carbon monoxid, sulfur dioxid and hydrogen sulfid. In carrying out the process with the use of steam the following reactions may oocur when the temperature of the retort chamber B is below 700 C.

If the gases escaping from the retort are conducted to the collector Q and thence into the condensing tower T the sulfur will be condensed and any sulfur dioxid present will combine with the hydrogen sulfid in the presence of a water spray. If desired to accelerate the combination in the presence of the water spray the latter may contain a catalyzing salt such as calcium chlorid the reaction taking place in the presence of the catalyzing agent will be as follows:

However, when the temperature of the retort B is above 700 C. another reaction than that above mentioned will occur since in this case the iron in the sulfid will almost instantly decompose water vapor admitted or present naturally and the reaction taking place will be as follows:

This is due to the fact that the affinity of iron at this temperature is greater for oxygen than for sulfur or that of hydrogen for sulfur, thus the hydrogen set free will unite with oxygen in preference to sulfur. The union of hydrogen and oxygen occurring higher up in the retort increases the area of high temperature to a considerable extent and the retort may be so controlled that practically no sulfur is discharged as sulfureted hydrogen or sulfur dioxid, or the gases discharged may consist of sulfur, sulfur dioxid, or hydrogen sulfid which are capable of being united outside of the retort in any one of several well known ways. The object of combinin the various ste s hereinbefore enumerated is to increase tiie quantity of sulfur obtained. Attention is called to the fact that no fuel is used except that which is present as a natural constituent of the raw material to be treated.

In connection with the operation of the apparatus, other than the retort, it is pointed out that the collector Q, is preferably a metallic barrel lined with brick so as to minimize corrosion and maintain the temperature of the gases so that the sulfur may not be condensed at this particular point in the process. .The condenser or washer is so arranged that the gases enter at the bottom and -progress upwardly through the material contained therein and are met by the spray. This part of the apparatus is preferably a metal cylindrical stack.

If instead of addingsteam to the retort it is desired to carry out the process in another way the pyrite or marcasite may be burned in such a manner as to cause 50 to 60% or more of the sulfur present in the pyrite to be discharged as sulfur and the remainder, except that remaining in the cinder or ash, to be discharged as sulfur dioxid. In carrying out this process the gases are passed through the collector Q to remove suspended dust by precipitation as before and are then passed into a retort or .cium sulfite. The temperature of this retort natural gas or other hydrocarbon being admitted through the valve in the main .lF to decompose the sulfur dioxid. The reaction taking place being as follow:

This reaction occurs indirectly by. the breaking down of the calcium sulfite into calcium oxysulfid through the action ofv the hydrocarbon, and the sulfur dioxid builds the oxysulfid up again to sulfite as follows:

The sulfur is extracted from the sulfur dioxid by removing the oxygen to produce water and carbon dioxid which maintains the temperature. The sulfur set free is vaporized and the sulfur coming fromthe retort along with the sulfur dioXid simply passes through the furnace. It is therefore evident that this furnace must be air tight or the sulfur would be oxidized.

While in the foregoing l[ have described a specific apparatus for carrying out, the

process hereinafter claimed, it is to be un-' ering sulfur from pyritic material which consists in heating the ore to drive ofi' sulfur dioxid, passing said sulfur dioxid through a container, heating said container from-within through the use of open flame gas jets, and finally introducing illuminating gas into the container whereby combustion may take place in the formation of sulfur, carbon dioxid and water.

3. The herein described process of recovering sulfur from pyritic material which consists in heating the ore to drive ofi' sulfur dioxid, passing said sulfur dioxid through a container, heating said container, and finally passing a gaseous hydrocarbon through said "container in the presence of a catalytic agent whereby combustion takes place with the formatlon of sulfur, carbon dioxid and water.

4:. The herein described rocess of recovering sulfur from pyritic material which consists in heating the ore to drive ofl' sulfur dioxid, passing the sulfur dioXid through a container having therein a mixture of calcium sulfid, and calcium sulfite, heating the interior of the container through the medium of open flame gas jets, and finally passing a gaseous hydrocarbon through said contamer whereby combustion takes place with the formation of sulfur, carbon dioxid and water.

5. The herein described process for regulating the combustion of pyritic material for-the recovery of sulfur therefrom which consists in placing the material in a container which is higher than its width, igniting the material at the bottom thereof, and withdrawing the material from the bottom after combustion has been completed continuously to permit'the downward feeding of material toward the heated zone.

' In testimony whereof ll affix my signature in presence of two witnesses.

ADDISON 1F. HOFFMAN. Witnesses:

JENNJUE JoNns, E. D. Wetsuit. 

